The invention discloses a quick-freezing device and a quick-freezing method based on an ultra-low-temperature water medium. The device is composed of two tank containers, a water pump, a water valve, a water pipe, a vacuum pump, an air valve and an air pipe. By virtue of the negative pressure of a water surface or by adding salt into water, the freezing point temperature of the water is reduced, ultra-low-temperature water cooling liquid is produced and circulates between to-be-frozen bagged freezing bodies, and the effect of quickly freezing the bagged freezing bodies is achieved. The device and the method can be used for quickly freezing bagged food such as aquatic products including crayfish and fish and medical products including bagged blood, the freezing speed is high, and the energy consumption is low.